The umbilical cord around the baby’s neck was choking her, turning the newborn blue Monday, when a Nassau police medic stepped in and delivered life, authorities said.

The rescue started when First Precinct officers tried to help a pregnant woman who was in pain and had trouble walking at her Henry Street home in Uniondale, Nassau police said.

They got the woman, 32, into an ambulance, where police medic Brian Matthews realized her water had broken, authorities said.

But the baby was coming into the world being with the cord that bound her to her mother wrapped around her neck, police said.

Matthews was able to remove the cord from the infant’s neck, police said, and the girl was born healthy in the back of the ambulance about 1:30 p.m.

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Authorities said police escorted the ambulance to a hospital, where mother and daughter were doing fine Monday.

Matthews declined to comment. Nassau police said they planned a news conference Tuesday with the officer to provide details of the rescue.